JP2577434B2 - Drill point molding die and molded product using the molding die - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molding die for forming a drill point by cold forging, and a molded product using the molding die.

(Prior Art and Problems to be Solved by the Invention) Conventionally, a drill point is formed by cold forging.
12 Using a molding die shown in FIG. 14, a drill point 25 of a drilling tapping screw 22 (FIGS. 15 to 21) is used.
(Fig.).

That is, the molding die has two grooves on the mating surface.
A set of forming dies 10, 12 each engraving forming recesses 12, 12 corresponding to the half shape of a drill point 25 having 28, 28;
It consists of eleven.

The shaping recess 12 has an inner surface 13 forming a cylindrical portion 26 of a drill point 25, a bottom surface 14 forming an inclined end surface 27 of the drill point 25, and a bulging portion 15 forming a groove 28 of the drill point 25. It is composed of

14a is an edge forming the cutting edge 27a of the drill point 25, 14b is an edge forming the chisel edge 27b, and 16 is a relief surface.

In FIGS. 18 and 19, reference numerals 23 and 24 denote a head and a shaft of the drilling tapping screw 22, respectively.

However, according to the forming die according to the conventional example, when the forming dies 10 and 11 are abutted to form the drill point 25 at the end of the work material 20 by cold forging, the cutting edge has a thickness of 0.03 to 0.
After molding by leaving a blank of 08 mm, the surplus material was removed in the next step. Then, in this case, when the cutting edge 27a of FIG. 14 serving as a drill blade tip is enlarged and viewed, it does not become as shown in FIG. 22 showing an ideal shape, but, for example, as shown in FIG. There was a problem that a 0.06 mm ultra-small blade tip 27e was generated and the drillability of the drill point 25 was reduced.
This is because, in a conventional molding die, material escapes during forging.

As a second problem, as the diameter of the drill increases, there is a problem that unless the rotation speed of the pinch pointer machine during the forming of the drill point is extremely reduced, the mold is broken. Specifically, if the rotation speed is 300 rpm when the drill diameter d is 2.9 mm, the life of the mold is short unless the rotation speed is set to 150 rpm, which is a half of the above, when the drill diameter is 3.9 mm. became.

On the other hand, the drill body diameter d ₁ is the minor axis of the substantially elliptical formed when butt forming dies 10, 11 according to prior art,
It is smaller than the diameter d ₂ of the workpiece material 20 (Figure 14). For example, the drill body diameter d ₁ when the forming dies 10, 11 are butted together
Is 3.4 mm, the diameter d ₂ of the work material 20 is 3.8 mm, and the drill body diameter d ₁ is about 10% of the diameter d ₂ of the work material 20.
Millimeters small. This is because, unless the work material 20 is pressed and clamped between the inner side surfaces 12 and 12, the work material 20 as a whole escapes upward, and the lower end of the work material 20 is torn off as shown in FIG. Because.

On the other hand, as shown in FIG. 23, forming dies 10 and 11 have forming recesses 12 in which the drill diameter d decreases toward the upper part.
There is also a conventional example in which a work material is formed to prevent the work material from escaping upward.

However, in this method, the forming recess 1 of the forming dies 10 and 11 is not used.
Since a large load is applied to the whole 2 and a force is applied to expand the molding recess 12, the mold is easily broken at an early stage. In short, easily cracked as the drill barrel diameter d ₁ is less smaller than the diameter d ₂ of the work material 20, if large Conversely, approached sawtooth shape as leading end portion of the drill point is shown in FIG. 20, well shaped Can not. Therefore, the diameter of the work material 20
the balance of d ₂ and the drill body diameter d ₁ becomes a problem.

As a countermeasure, as shown in Fig. 24, forming dies 10, 1
Pressing surface 30 may be applied to each 1 (forming die 10
Is not shown).

In any case, however, there is a problem of chipping of the micro blade and life of the mold. This is because when the forming dies 10 and 11 are abutted, the work material 20 slightly rotates around its axis as shown by the arrows in FIGS. 14 and 24, and the material of the cutting edge is substantially obliquely upward. This is because the tip of the micro blade is chipped. This is because the metal material located above the edge 14a is easy to move because the press resistance of the bulging portion 15 is strong.

The present invention has been made in view of the above problems, and provides a molding die capable of forming the drill point without chipping of the extremely small blade tip and having high productivity, and also provides a molded product having a drill point excellent in drilling property. The purpose is to:

(Means for Solving the Problems) In order to achieve the former object, a forming die for a drill point according to the present invention is formed by a pair of forming dies 10, 11 in which forming recesses 12 are engraved on abutting surfaces. The inner surface 13 corresponding to the cylindrical portion 26 of the drill point 25, and the bottom surface forming the inclined end surface 27 of the drill point 25.
In the forming die of the drill point 25 composed of 14 and the bulging part 15 forming the groove part 28 of the drill point 25, the drill body diameter d _1, which is the minor diameter of the inner surface 13 of the forming dies 10, 11 butted against _{each other.} but with greater than or equal to the diameter d ₂ of the work material 20, the corner portion formed of the bottom surface 14. and the inner surface 13, the intersection V ₁ of the end edge 14b and the shaft center 30 to form a chisel edge 27b 45% ± 10 of the drill diameter d, which is the major diameter of the inner surface 13 from
% Only from the starting point V ₃ of the bulging portion 15 located above the step portion 17 consisting substantially parallel to the withdrawn twill line portion 17a to the edge 14a to form the cutting edge 27a of the drill point 25 and projecting There is a configuration.

In order to achieve the latter purpose, the molded product has a configuration in which one end has a drill point 25 formed in the molding recesses 12, 12 of the molding dies 10, 11.

(Operation) Therefore, according to the present invention, when the butting surfaces of the forming dies are butted against each other and cold forging is performed, the stepped portion 17 provided in the forming recess prevents the above-mentioned material from escaping in the rotational direction and the upward direction of the work material. Drill point with a cutting edge that helps to form a cutting edge having a sufficient rake angle and rake face, and furthermore, a step provided near a predetermined tip cutting edge makes the metal structure of the cutting edge dense, and a micro-edge without chipping. Can be formed.

Embodiment An embodiment according to the present invention will be described below with reference to the accompanying drawings of FIGS.

The molding die of the drill point according to claim 1 is substantially the same as the above-mentioned first conventional example, except that a corner formed by the inner side surface 13 and the bottom surface 14 of the molding recess 12 has a stepped portion. 17
That is to protrude.

That is, the step portion 17 has a twill line portion 17a that is substantially parallel to the edge 14a that forms the cutting edge 27a of the drill point 25, and is continuous with the bulging portion 15. And chisel edge 27b
The intersection between the edge 14b and the axis 30 is V ₁ , the intersection between the bulge 15 and the lower side of the vertical plane of the step 17 is V ₂ , the bulge 15 and the twill line
Assuming that the intersection with 17a is V ₃ , and the intersection between the bulging portion 15 and the upper side of the step 17 is V ₄ , the vertical distance K ₁ from the point V ₁ to the point V ₂ is the major diameter of the inner surface 13. 30% of the drill diameter d, the vertical distance K ₂ from the point V ₁ to the point V ₃ 45% of the drill diameter d, the vertical distance K ₃ from the point V ₁ to the point V ₄ is preferably 75% of the drill diameter d The above-mentioned distances may be changed by about ± 10% depending on the size of the work material.

To the vertical distance K ₂ and 45% ± 10% of the drill diameter d is 35
If the amount is less than 50%, the arc material starts to have chipped edges, and if the amount exceeds 55%, the life of the molding die begins to decrease.

Further, the protruding dimension H varies depending nominal diameter of the cylindrical portion 26 against the side of the stepped portion 17, 25% ± 10% of the drill barrel diameter d ₁ is preferred. If it is less than 15%, chipping of the micro blade starts to occur in the work material, and if it exceeds 35%, the rotation speed of the pinch pointer must be reduced.

Furthermore, the twill line portion 17a of the step portion 17 may be substantially parallel to the edge 14a, but the inclination angle may be wider than the edge 14a by about 10 degrees. This is because, when spread out in this manner, chipping of the very small cutting edge is less likely to occur in the portion 27c (see FIG. 7) of the tip cutting edge 27a that is the outermost periphery.

Because, when the angle is increased, the area of the vertical surface constituting the step portion 17, particularly, the area on the outer peripheral side increases, so that when the forming dies 10, 11 are abutted, the load applied to the work material 20, especially This is because the load on the outer peripheral side is increased, the density of the work material 20 near the outer peripheral side is increased, and chipping of the very small blade tip is less likely to occur. For this reason, there is obtained an advantage that the chipping of the very small blade near the outer peripheral portion, which is particularly likely to occur, can be prevented.

The bulging portion 15 has a conical convex surface, and a radius may be appropriately provided at each corner and corner. Furthermore, the drill diameter d should be at equal to or greater than the drill body diameter d _1.

In the case where the drill point 25 is formed by the forming die according to the present embodiment, as shown in FIG.
The drill trunk diameter d _1, is slightly larger than or equal to d ₂ and the diameter d ₂ of the work material 20. In this way, when the forming dies 10, 11 are forged against each other, even if the inner surfaces 13, 13 of the forming dies 10, 11 come into contact with the work material 20, they do not come into pressure contact with each other, but merely come into contact.

When the step 17 hits the work material 20, the rotational direction and upward escape of the work material 20 are regulated, and the metal material does not escape, so that the metal structure constituting the cutting edge becomes dense. As a result, chipping of the very small cutting edges of the cutting blades 27a and 27c is eliminated, and the performance of the drill point is improved.

In addition, since it is not necessary to plastically deform the cylindrical portion 26 of the drill point 25 as in the conventional example, the load required for forming the drill point 25 is small, while the load applied to the molding die is small. Therefore, there is an advantage that the fatigue of the molding die is reduced and the life thereof is extended.

On the other hand, examples of the molded product formed by the molding dies 10 and 11 include a bolt and a drilling device for a blind rivet, in addition to the drilling tapping screw 22 shown in FIGS. 7 to 11.

 Reference numeral 29 denotes a concave portion formed by the step portion 17.

In addition, chip 21 (6th
If the figure) is left behind at the drill point 25, it is possible to prevent the cutting edge 27a from being deformed by a collision occurring during transportation and becoming a defective product before quenching.

Experimental Example 1 drill diameter d is 3.5 mm, the drill body diameter d ₁ is 3.4 mm, 31% of the K ₁ is a drill diameter, K ₂ 45% of the drill diameter, 80 K ₃ is the drill diameter
%, H is 20% of the drill diameter, and the shaft diameter is 3.3mm
Drilling tapping screw 22 with a nominal diameter of 4 mm from the workpiece material
When drill point 25 is formed with a pinch pointer,
In the molding die according to the present invention, the rotation speed is about 1 at 450 rpm.
After 500,000 forgings were performed, the mold was damaged.

Comparative Example 1 Except that a step was provided, except that a drilling point 25 was formed at the end of a work material having a shaft diameter of 3.3 mm using a molding die having the same outer diameter as that of Experimental Example 1, except for the comparative example. In such a mold, the mold was damaged after about 1 million forgings were performed at a rotation speed of 300 rpm.

Since the number of molds that can be formed has increased from about 1 million to about 1.5 million, it was found that the life of the mold was improved by 50%.

In addition, the number of rotations of the pinch pointer is from 300 rpm to 450 rpm.
Since it can be increased to pm, it was found that productivity was improved by 50%.

This is because, in the molding die according to Experimental Example 1, only a portion of the drill point 25 other than the cylindrical portion 26 need only be plastically deformed, so that a large load is not required. For this reason, when forging with a pinch pointer, it is considered that the number of rotations can be increased, the load applied to the molding die is reduced, and fatigue is reduced.

Experimental Example 1 of molding with the molding die according to the present invention
A drilling tapping screw having a drill point according to JIS B1125- and a drilling tapping screw having a drill point formed by a molding die according to a conventional example.
Based on 1984, a drilling test (10 samples each) was performed on a 1.6 mm thick steel plate with a thrust of 15 kg. The average time required for drilling tapping screws, which required the time required for drilling, was 1.06 seconds. On the other hand, in the case of the conventional example, it was 1.80 seconds, indicating that the piercing property was improved by 41%.

This is because the step provided in the forming recess at the time of forging regulates the material escape in the rotating direction and the upward direction of the work, making the metal structure of the cutting edge dense and preventing chipping of the micro blade tip. it is conceivable that.

(Effects of the Invention) As is clear from the above description, according to the molding die according to the present invention, at the time of forging, the step provided in the molding recess allows the material to escape in the rotation direction and the upward direction of the work material. , The metal density of the cutting edge portion is increased, and chipping of the very small edge of the cutting edge is prevented, so that a molding die having better performance than conventional ones can be obtained.

Also, since only the portion of the drill point excluding the cylindrical portion is only plastically deformed, the contact area is smaller than when the cylindrical portion is also plastically deformed as in the conventional example, and the load on the molding die is reduced. The load to be applied becomes smaller.
For this reason, for example, when forging with a pinch pointer or the like, the number of rotations can be increased, so that productivity is improved.

In addition, since the applied load is reduced, the load applied to the molding die is reduced, so that fatigue failure of the molding die hardly occurs and the life of the molding die is extended.

[Brief description of the drawings]

1 to 6 show an embodiment of a molding die for a drill point according to claim 1, FIG. 1 is a front view of the molding die, and FIG. 2 is a sectional view taken along the line II-II of FIG. FIGS. 3 and 4 are plan views, FIGS. 4 and 5 are perspective views of a forming die, FIG. 6 is a cross-sectional view showing a state of working with the forming die, and FIGS. An example of such a molded product is shown,
7 and 8 are front and side views of the drill point, FIG. 9 is a bottom view of the drill point, FIGS. 10 and 11 are front and plan views showing a cross-drilled drilling tapping screw, 12 to 14 show one embodiment of a molding die for a drill point according to a conventional example, FIGS. 12 and 13 are perspective views of a molding die, and FIG. 14 shows a state of working with the molding die. FIG. 15 to FIG. 21 show an embodiment of a molded product according to a conventional example. FIG. 15, FIG. 16 and FIG. 17 are front views, side views and bottom views of drill points, and FIG. FIGS. 19 and 20 are a front view and a plan view showing a cross-drilled drilling tapping screw, FIG. 20 is a front view of an essential part, FIG. 21 is an enlarged view of an essential part, and FIG. Enlarged views, FIGS. 23 and 24 are front views showing another embodiment of the molding die according to the conventional example. Figure and is a cross-sectional view. 10,11 ... forming die, 12 ... forming recess, 13 ... inner side surface, 14 ... bottom surface, 14a, 14b ... edge, 15 ... bulging part, 17
... Step, 17a ... Twill wire, 22 ... Drilling tapping screw (molded product), 25 ... Drill point, 26 ... Cylindrical part, 27 ... Inclined end face, 27a, 27c ... Cutting edge, 27b … Chisel edge, 28… groove, 30… axis.

Claims (2)

(57) [Claims] 1. A set of forming dies (10) and (11) each having a forming recess (12) engraved on an abutting surface, said forming recess (12) being a cylindrical portion of a drill point (25). (2
6) inner surface forming (13) and drill point (25)
The bottom (14) forming the inclined end surface (27) and the bulging portion (15) forming the groove (28) of the drill point (25) are formed in a molding die for the drill point (25). It said forming die (10), together with the drill body diameter d ₁ is the minor axis of the inner surface (13), is greater than or equal to the diameter d ₂ of the work material (20) in (11), the inner surface ( 13) and the bottom surface (14), a corner (14b) forming a chisel edge (27b) and an axis (3
0) and bulge located above only 45% ± 10% of the drill diameter d is diameter of the inner surface from the intersection point V ₁ (13) of the origin of (15)
From V _3, that the stepped portion composed of cutting twill line portion substantially drawn parallel to edge to form the (27a) (14a) (17a) of the drill point (25) to (17), projecting from Drill point (25) forming die. 2. A drill having at one end a drill point (25) formed by a forming recess (12), (12) of a forming die (10), (11) according to claim 1. Molded product using the molding die at point (25).